I came across a tech article in an issue of the Continental Comments from years ago- it said to be real careful about rebuilt water pumps because if the rebuilder replaced the rear cover bolts with standard head-size bolts it will interfere with the timing cover and may have pushed it in in your case. The solution was to grind down the bolt heads. It's good advice that can be easily overlooked.

A rebuild pump I recently purchased. Note the replacement bolts with red X vs. the original bolts.